Hydraulic drive device

Abstract

This hydraulic drive device supplies a working fluid to a hydraulic cylinder including a head-end port and a rod-end port and includes: a hydraulic pump motor including a suction port and a discharge port; an electric motor connected to the hydraulic pump motor; a directional control valve that switches a connection target of the head-end port between the discharge port and the suction port; a regeneration valve that opens and closes a regeneration passage connecting the head-end port and the rod-end port; and an unloader valve that connects, to a tank, a discharge passage connecting the discharge port and the directional control valve.

1 . A hydraulic drive device that supplies a working fluid to a hydraulic cylinder including a head-end port and a rod-end port, the hydraulic drive device comprising:
 a hydraulic pump motor including a suction port and a discharge port;   an electric motor connected to the hydraulic pump motor;   a directional control valve that switches a connection target of the head-end port between the discharge port and the suction port;   a regeneration valve that opens and closes a regeneration passage connecting the head-end port and the rod-end port; and   an unloader valve that connects, to a tank, a discharge passage connecting the discharge port and the directional control valve.   
     
     
         2 . The hydraulic drive device according to  claim 1 , further comprising:
 a control device that controls an operation of each of the directional control valve, the regeneration valve, and the unloader valve according to a signal that is input to the control valve.   
     
     
         3 . The hydraulic drive device according to  claim 2 , wherein:
 in causing the directional control valve to connect the head-end port to the suction port, the control device causes the unloader valve to connect the discharge passage to the tank.   
     
     
         4 . The hydraulic drive device according to  claim 2 , wherein:
 in causing the directional control valve to connect the head-end port to the suction port, the control device causes the regeneration valve to open the regeneration passage and when a predetermined condition is satisfied, reduces an opening degree of the regeneration valve.   
     
     
         5 . The hydraulic drive device according to  claim 2 , wherein:
 in causing the directional control valve to connect the head-end port to the suction port, when a predetermined condition is satisfied, the control device causes the directional control valve to reduce an opening degree between the head-end port and the suction port.   
     
     
         6 . The hydraulic drive device according to  claim 4 , further comprising:
 a temperature sensor that measures a coil temperature of the electric motor, wherein:   the predetermined condition is that the coil temperature measured by the temperature sensor is higher than or equal to a predetermined temperature.   
     
     
         7 . The hydraulic drive device according to  claim 4 , further comprising:
 a suction-end pressure sensor that measures inflow pressure that is hydraulic pressure at the suction port of the hydraulic pump motor, wherein:   the control device calculates an inflow load on the hydraulic pump motor according to the inflow pressure measured by the suction-end pressure sensor; and   the predetermined condition is that the inflow load is greater than or equal to a predetermined value.   
     
     
         8 . The hydraulic drive device according to  claim 5 , further comprising:
 a temperature sensor that measures a coil temperature of the electric motor, wherein:   the predetermined condition is that the coil temperature measured by the temperature sensor is higher than or equal to a predetermined temperature.   
     
     
         9 . The hydraulic drive device according to  claim 5 , further comprising:
 a suction-end pressure sensor that measures inflow pressure that is hydraulic pressure at the suction port of the hydraulic pump motor, wherein:   the control device calculates an inflow load on the hydraulic pump motor according to the inflow pressure measured by the suction-end pressure sensor; and   the predetermined condition is that the inflow load is greater than or equal to a predetermined value.